Technical Abstract:
The initiative to use plant pathogens and allelochemicals from pathogens and other microorganisms as biological weed control agents (bioherbicides) began about thirty years ago. Since then, numerous plant pathogens (bacteria and fungi) and microbial allelochemicals have been isolated, identified, and tested for their bioherbicidal potential. Pathogens (and in some cases microbial phytotoxins) may be used directly on target weed species, or such allelochemicals may provide unique chemical templates for the synthesis of new herbicide classes with novel molecular modes of action. To date, the most successful microbial products that have led to the development of commercialized herbicides are bialaphos (commercially available in Japan) and glufosinate (marketed world-wide). Glufosinate is the ammonium salt of phosphinothricin, which is the active ingredient of bialaphos derived from non-phytopathogenic Streptomyces species. This overview will examine some selected advances in the isolation and identification of novel plant pathogens that have weed target hosts, and some microbial allelochemicals with phytotoxic properties. Perspectives on the use of these bioherbicides in weed control, and on their allelopathic interactions with plants and other microorganisms are also discussed.